Method and apparatus for taking cores from a borehole



March 9, 1937. H. M. HOHMANN ET Al. 2,073,263

METHOD AND APPARATUS FOR TAKING coREs FROM A BoRE HOLE Filed MaICh 29, 1935 2 Sheets-Sheet l larch 9, 1937. H. M. HOHMANN ET A1. 2,073,263

METHOD AND APPARATUS FOR TAKING OOREs FROM A BORE HOLE Filed March 29, 1935 2 sheets-Sheet 2 izatented Mar. 9, 1937 PATENT l GFFICE BEETHOD AND APPARATUS FOR TAKING @DRES FROM A BOREHOLE Henri M. Hohmann and Hendrik N. L. C. E. C. de Wilde, '.lhe Hague, Netherlands, assignors to Shell Development Company, San Francisco,J

a corporation of iDelaware Application March 29, 1935, Serial No. l3,728 En the Netherlands January 23, 1935 6 Claims.

In deepr drilling it is usual to take cores from the hole in order to examine the strata drilled through. With the aid of a hollow core drill a ore is drilled out of the surrounding rock at the bottom of the hole and taken up inside the drill pipe, generally in separate core barrel inside the drill pipe, after which it is drawn up together with the bit and the drill pipe. This manner of withdrawing the core naturally takes much time, and consequently various constructions have already been proposed to render it possible to draw up the detached core barrel with the core through the drill pipe separately and to let down an empty core barrel through the pipe into the drill to take up a fresh core. This, however, leads to rather complicated constructions.

The invention provides a new method for drawing cores in hush-drilling and drilling-apparatus with which the method can be applied.

According to the invention the stream of ilush liquid is utilized for bringing up the core. To this end-contrary to the normal operation--the stream of flush liquid is introduced into the well round the outside of the drill pipe. The pressure exerted by the liquid breaks the connection between the core and the bit head', after which the core is carried up with the flush liquid `in the drill pipe.

barrel; or it may be detached from the bit head and brought up with the core.

The invention will be further explained with reference to the drawings, which give two examples of a core drill for rotary drilling accorddrilling out a core, the form of the cutting or drilling members proper being, of course, arbitrary. Into the intermediate piece 2 the core barrel is screwed, which leaves sufcient space between its outer wall and the inside of the drill` The core barrel may remain iixed to the bit head, the core then being forced out of thebottom of the core barrel are provided a number of core-catching members f8 in the form of springs, carried by a ring l.

Between the core barrel and a part of the drill pipe, e. g. the intermediate piece 2, is a downwardly opening valve, which in the drawings is designed as an annular valve ld, which is pressed upwardly against the seat Ei-designed as a double ring-by the helical spring ll.

During normal drilling, iiush liquid is pumped down through the drill pipe in the usual way, the liquid pressure keeping valve 5 closed and opening valve lil against the pressure of spring it, so that the ush'liquidcan pass out through the passages l2 into the hole, in which it rises. As the drillingv proceeds, a core enters the core barrel d, the liquid displaced by the core escaping from the core barrel through valve 5.

When it is desired to remove the core from the core barrel the direction of the circulation of the ush liquid is reversed, i. e. the liquid is then pumped into the space between the drill pipe and the wall of the hole,`it being necessary, of course, to close this space temporarily at the top, for instance by means of a blow-out valve. The pressure exerted by the liquid and the action of spring ll keep valve l0 closed, so that no liquid can escape through the said Valve. Thus the full pressure prevailing'within the Hush liquid comes to bear on the bottom of the core, which has been previously detached from the mother rock. Under the action ofthis pressure the core is brought up out of the core barrel, opens valve 5, and is carried up further through the drill pipe, at the top of which it is caught. Care has to be taken, of course, that the passage through the drill pipe is nowhere narrower than the diameter of the core, but rather some play should be left. The layer o flush liquid between the core and the wall oi the drill pipe prevents too much erosion of the core and serves in a certain sense as a lubricant.

instead of a construction as illustrated in Fig. l, a design can be chosen in which the core barrel is brought up together with the core by the action of the :dush liquid. Such a construction is shown in Figs. 2 and 3, the former of which is subdivided into two parts joining up together.

The parts indicated in Fig. 2 by I, 2, 3, 1, 8, 9, I0, and Il are in principle identical with those indicated by the\correspondingl numbers in Fig. 1. However, in this construction the core barrel 4 is not permanently connected to the bit head and the drill pipe, but is detachably arranged Within a guide tube 20 connected to the drill pipe, said guide tube having a somewhatjunnel-shaped enlargement at the top. Below this enlargement tion as to allow a core to pass out of the core the core-barrel is sealed on the outside within the barrel in upward direction, and valve means guide tube. allowing a passage of fluid only from the interior 'I'he core barrel is closed at the top by a head 5 2| containing the usual ball valve 22 allowing the flush liquid contained in the core barrel to escape when a core enters the barrel. 'This head 2| carries also the mechanism holding the core barrel in place within the drill pipe during drilll0 ing. As shown on the drawings the head within a slot formed between two cheeks 24 carries a pawl 28 turning about a bolt 25, a spring 23 tending to rotate the pawl in a counter-clockwise direction.

'I'he movement of the pawl is limited by a pin 30. At its lower end the pawl has a cam or lip 21 which engages behind a collar 29 of the intermediate piece 28 forming part of the drill pipe, so that upward movement of the core barrel is prevented.

For releasing the pawl 26 use is made of a member 32, which is lowered into the drill pipe and moves downwards under the infiuence of its weight, if necessary assisted by the pumping pressure. Fig. 2 shows this member, constructed as a pipe closed at the top and equippedwith a valve 34 opening upwards for passage of the flush liquid,

at the time it has almost come into contact with the beveled top of pawl 26. With a continued downward movement of the releasing member 30 this member forces the top of the pawl 26 to the right until the lip 3| of the pawl engages behind the annular inward projection 23 provided at the underside of the releasing member. Thereby the lower end of the pawl has moved to the left, so that the lip 2l has become free of collar 29.

On the direction of flow of the flush liquid now being reversed the flush pressure will force the core barrel 4 upwards in the drill pipe, together with the releasing member 32.

A newcore barrel may be thrown or pumped down through the drill pipe and will be secured in place by the pawl 2i as soon as it has reached the proper position.

The members for securing and releasing the core barrel may, of course, be constructed in a manner dierent from that described and illustrated.

As shown in Fig. 4, the member 32 may be equipped at the top with a spring-loaded valve 35 opening downwards, which enables cleaning of the member 32, if clogged up internally, by means of a downward now of flush liquid.

' What we claim is:

l. A core drill comprising a core barrel of such shape and being provided at itsupper end with upwardly opening valve means of such construcof the drill outwardly to the space around the drill.

2. Core drill comprising a drill head with drilling members, a. core barrel connected to the drill head, a passage for drilling fluid situated around said core barrel and issuing at the outside of the head in the vicinity of said drilling members, and a downwardly opening check valve situated within said fluid passage.

3. Core drill comprising a drill head, a core.

barrel, means fordetachably connecting the core barrel to the drill head, fluid passages in said drill head and passing from the inside to the outside thereof, and means for preventing a passage of fluid through said passages in a direction from the outside of the drill head to the inside thereof.

4. Core drill comprising a drill pipe, a drill head connected to said drill pipe, a cylindrical open-ended guide tube with flaring upper end connected at its lower end to said drill head, means for detachably holding a core barrel within said guide tube, fluid passages extending through the drilling head and communicating at their inner ends with a passage formed between said drill pipe and said guide tube, and valve means arranged within the latter passage and allowing a passing of fluid only in a direction towards the iiuid passages in the drilling head.

5. A method for taking cores from a drill hole comprising drilling a core by means of a core drill attached to a drill pipe, said core drill comprising a core barrel, supplying a drilling fiuid to the core drill through the drill pipe and a valved passage outside the core barrel and removing said fluid from the hole outside the drill pipe, receiving the core drilled in the core barrel, reversing the circulation of the drilling fluid, closing the valved passage outside the core barrel to the flow of said fluid, forcing the core from the core barrel and lifting it to the surface through the drill pipe by the pressure of the drilling fluid applied to the bottom of the core.

6. A core drill comprising a drill pipe, a drill head, a core barrel, means detachably locking the core barrel with the drill head, said means being adapted to be released by the impact of a body dropped into the drill pipe, a vfluid passage between the core barrel and the core head, and valve means in said passage allowing the uid to pass only from the interior of the drill outwardly to the space around the drill.

HENRI M. HOHMANN. HENDRIK N. L. C. E. C. nr W1LDE. 

